Goal: Reduce contemporary markers of later-in-life risk of obesity-related disease in urban, middle school children by improving their diet and increasing their lifestyle physical activity. Specific Aims. 1. Recruit 125 mostly African American and Latino girls and boys (6th - 7th grades) from a randomly- selected urban middle school and enroll them in a culturally- tailored, community-based lifestyle change program designed to prevent obesity by preventing the insulin resistance syndrome; contrast their experience with 125 matched girls and boys attending a randomly-selected comparison school. 2. Implement a comprehensive, self-efficacy-enhancing, semester-long lifestyle change program to reduce risk of obesity by reducing risk factors comprising the insulin resistance syndrome. The program will promote eating more servings of vegetables, whole fruits, whole grains and more servings of reduced calorie density foods in the context of sustained increases in daily "lifestyle" physical activity (e.g., fun walks, architectural tours, hiking, etc.). The semester-long program includes weekly 30-minute walks and brief discussion sessions in a variety of community venues about the challenges and benefits of better eating choices and increased lifestyle physical activity. Trained peer role models, selected parents and adult facilitators will provide sound advice for eating better and doing more frequent, enjoyable physical activity. Within resource constraints, the program will attempt to be multi-level, involving parents, teachers, coaches, food service staff, peers as well as study participants. 3. Evaluate program effectiveness at 4+ months follow-up (end of the semester), 12 and 18 months follow-up. Primary outcomes are serum HbA1c and BMI; secondary outcomes are serum total cholesterol, 1-mile run, dietary self-report, physical activity self-report. Mediating variables are self-report behaviors and attitudes. 4. Compile and distribute a resource book that includes those behavior change strategies that were observed to work best with this population.